oxidative addition of alkyl halides to chiral cyclometallated platinum(ii) complexes with thienyl...

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Journal of Organometallic Chemistry 604 (2000) 178–185

Oxidative addition of alkyl halides to chiral cyclometallatedplatinum(II) complexes with thienyl imines. X-ray crystal structure

of [PtMe{3-((S)-PhCHMeNCH)C4H2S}SMe2]

Craig Anderson a,b, Margarita Crespo c,*, Merce Font-Bardıa d, Xavier Solans d

a Orgometa Laboratories, 6254 St. Denis, Montreal, Canada H2S 2R7b Research and De6elopment Di6ision, CRG Laboratory, PO Box 301, Succ. R, Montreal, Canada H2S 3K9

c Departament de Quımica Inorganica, Facultat de Quımica, Uni6ersitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spaind Departament de Cristal.lografia, Mineralogia i Diposits Minerals, Uni6ersitat de Barcelona, Martı i Franques s/n, E-08028 Barcelona, Spain

Received 28 February 2000; received in revised form 16 April 2000

Abstract

The reaction of [Pt2Me4(m-SMe2)2] with ligand 3-((S)-PhCHMeNCH)C4H3S (1) produced the chiral cyclometallated compound[PtMe{3-((S)-PhCHMeNCH)C4H2S}SMe2] (2) which was characterized structurally. The reactions of 2 with phosphines gavecompounds [PtMe{3-((S)-PhCHMeNCH)C4H2S}L] (L=PPh3 (3), P(2-MeC6H4)3 (4), Ph2PCH2CH2PPh2 (5)). The oxidativeaddition of methyl iodide to compounds 2 and 3 gave two diastereoisomers each of compounds [PtMe2I{3-((S)-PhCH-MeNCH)C4H2S}L] (L=SMe2 (6a/6a%), PPh3 (7a/7a%)) in a ratio 2.1:1 and 2.4:1, respectively. Subsequent isomerization gave, ineach case, a new pair of diastereoisomers. Compounds 4 and 5 failed to react with methyl iodide, while platinum(II) compounds[PtX{3-((S)-PhCHMeNCH)C4H2S}PPh3] (X=I (8), Br (9)) were obtained in the reactions of 3 with ethyl iodide or benzylbro-mide. © 2000 Elsevier Science S.A. All rights reserved.

Keywords: Platinum; Thienylimines; Cyclometallation; Chirality; Crystal structure; Oxidative addition

1. Introduction

Oxidative addition reactions of organoplatinum com-plexes with nitrogen-donor ligands have been reviewedrecently [1]. The reactions with organohalides usuallygive the products of trans oxidative addition. Some-times, the cis isomer is formed by a competitive cisoxidative addition pathway, or it may be formed bytrans oxidative addition with subsequent isomerizationof the platinum(IV) product to the more stable cisisomer. In particular, cyclometallated platinum(II)compounds are good candidates in oxidative additionreactions of alkylhalides due to the presence of Pt�Nand Pt�C s bonds which increase the electron densityat the metal center [2,3]. Square planar platinum(II)

complexes are inherently achiral but due to increasinginterest in chiral inorganic compounds related to enan-tiomeric catalysis, bioinorganic chemistry andsupramolecular chemistry, the introduction of chiralityin such compounds has been analyzed. This can beachieved when chiral ligands are involved, or whensteric hindrance produced an helical distortion, asshown for cis-bis-cyclometallated compounds [4,5].Studies of oxidative addition reactions to both types ofchiral cyclometallated platinum(II) compounds havebeen reported recently [6–8].

We have studied previously the oxidative additionreactions of methyl iodide to compounds [PtMe{3-(PhCH2NCH)C4H2S}L] (L=SMe2 or PPh3), and theobserved differences in the stereochemistry of the finalproducts were explained by the different bulk of theligand L [9]. In this paper we report the results obtainedfor the analogous chiral complexes [PtMe{3-((S)-PhCHMeNCH)C4H2S}L].

* Corresponding author. Tel.: +34-93-4021273; fax: +34-93-4907725..

E-mail address: [email protected] (M. Crespo).

0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.PII: S 0 0 2 2 -328X(00 )00231 -X

C. Anderson et al. / Journal of Organometallic Chemistry 604 (2000) 178–185 179

2. Results and discussion

2.1. Syntheses and crystal structure of compound 2

Ligand 3-((S)-PhCHMeNCH)C4H3S (1) was pre-pared from the condensation reaction of 3-thiophene-carboxaldehyde and (S)-methylbenzylamine in ethanol.The reaction of this ligand with [Pt2Me4(m-SMe2)2] pro-duced cyclometallated compound [PtMe{3-((S)-PhCH-MeNCH)C4H2S}SMe2] (2) as a single isomer arisingfrom intramolecular activation of a C�H bond of thethiophene ring, followed by methane elimination in asimilar process to that reported for analogous systems[10,11].

Compound 2 was characterized by elemental analysesand 1H-NMR spectroscopy. Three distinct resonancesappeared in the methyl region corresponding to themethyl group bound to platinum (2J(Pt�H)=79 Hz),to the dimethylsulfide ligand (2J(Pt�H)=32 Hz), and

to the methyl substituent of the benzyl group. Thevalue of the coupling of the imine hydrogen to plat-inum (2J(Pt�H)=51 Hz) indicates the formation of ametallacycle [10,11], while the observed J(H�H) valuefor the mutual coupling of the thienyl hydrogens im-plies that the activation of the C�H bond took place atthe a-position [12].

Suitable crystals of compound [PtMe{3-((S)-PhCH-MeNCH)C4H2S}SMe2] (2) were grown in acetone solu-tion. The crystal structure is composed of discretemolecules separated by van der Waals interactions. Thestructure is shown in Fig. 1, and confirms the geometryexpected. In particular, the methyl group is trans to thenitrogen atom, the C�N group is endo to the cycle andthe stereochemistry of the asymmetric carbon is S. Theimine adopts an (E)-configuration, the torsion angleC(6)�N�C(5)�C(2) being −176.4°. The platinum atomdisplays a tetrahedral distorted planar coordination andthe following displacements (A, ) are observed from theleast-squares plane of the coordination sphere: Pt,0.023; S(2), −0.055; N, 0.056; C(1), −0.075; C(16),0.051. The metallacycle is approximately planar — thelargest deviation from the mean plane determined bythe five atoms is 0.018 A, for C(2) — and nearlycoplanar with the coordination plane, the dihedral an-gle being 3.20°. Molecular dimensions are listed inTable 1. The angles between adjacent atoms in thecoordination sphere of platinum lie in the range 77.4–95.4°, the smallest angle corresponding to the metalla-cycle. Bond lengths in the coordination sphere of theplatinum and in the thiophene ring are in the usualrange for analogous compounds [7,13–15]. The metal-lacycle is smaller than for compound [PtMe{3-(PhCH2NCH)C4H2S}PPh3] [9] (perimeter 8.153 vs.8.309 A, ) which is consistent with the smaller size ofSMe2 versus PPh3 ligand. Moreover, in the latter struc-ture as well as in compound [PtMe{(S)-PhCHMe-NCHC6H3F-2}PPh3], the benzyl group lies away fromthe coordination plane in order to minimize the stericcrowding in the coordination sphere of the platinum,whereas for 2, the benzyl group lies towards the smallSMe2 ligand.

2.2. Reactions with phosphines

As shown in Scheme 1, the reaction of 2 withmonodentate phosphines produced compounds [PtMe-{3-((S)-PhCHMeNCH)C4H2S}L] (L=PPh3 (3), P(2-MeC6H4)3 (4)) which were characterized by elementalanalysis and 1H- and 31P-NMR spectroscopies. Thephosphine replaced the SMe2 ligand, and even with anexcess of phosphine, the metallacycle is not cleaved.

A single isomer is detected for compound 3 whilecompound 4 consists of two isomers (ratio 3:1), due tothe hindered rotation of the ortho-tolyl groups. In allcases, the methylplatinum resonance appears as a dou-

Fig. 1. Molecular structure of compound [PtMe{3-((S)-PhCH-MeNCH)C4H2S}SMe2] (2).

Table 1Selected bond lengths (A, ) and angles (°) in compound (2)

Bond lengthsPt�C 1.975(9) Pt�C(16) 1.997(9)

Pt�S(2)2.143(7)Pt�N 2.336(3)1.739(11) S(2)�C(14) 1.801(10)S(2)�C(15)

N�C N�C(6)1.295(11) 1.462(10)C(1)�C(2) 1.418(11)C(2)�C(5)1.322(13)

1.519(12) C(6)�C(13) 1.519(12)C(6)�C(7)

Bond anglesC(1)�Pt�C(16) C(1)�Pt�N92.9(4) 77.4(4)

C(1)�Pt�S(2) 171.3(3)C(16)�Pt�N 170.1(3)C(16)�Pt�S(2) 95.4(2)N�Pt�S(2)94.4(3)

109.9(4)C(15)�S(2)�Pt99.8(5)C(15)�S(2)�C(14)C(5)�N�C(6) 121.9(8)C(14)�S(2)�Pt 106.9(3)

112.2(6) C(6)�N�Pt 125.8(6)C(5)�N�Pt117.7(7)C(2)�C(1)�Pt 115.6(9)C(1)�C(2)�C(5)

111.1(7)N�C(5)C�(2) N�C(6)�C(7)117.0(8)114.1(7)N�C(6)�C(13) C(7)�C(6)�C(13) 108.9(8)

C. Anderson et al. / Journal of Organometallic Chemistry 604 (2000) 178–185180

Scheme 1. (i) Reaction with [Pt2Me4(m-SMe2)2] in acetone; (ii) reaction with the corresponding phosphine in acetone.

blet due to coupling with the phosphorus atom and isalso coupled to platinum. The imine hydrogen is cou-pled to platinum but not to phosphorus, which indi-cates a cis arrangement of the imine and the phosphine.For each isomer of compound 4, three distinct reso-nances appear for the methyl groups of the ortho-tolylphosphine.

Due to the chelating nature of the diphosphine, adifferent result was obtained when the reaction of 2with 1,2-bis(diphenylphosphino)ethane (dppe) was car-ried out under the same experimental conditions. In thiscase, both the SMe2 ligand and the nitrogen of theimine ligand are displaced from the coordination sphereof the platinum. Consequently, the metallacycle iscleaved and the imine acts as a [C−] monodentateligand. Compound [PtMe{3-((S)PhCHMeNCH)-C4H2S}(Ph2PCH2CH2PPh2)] (5) was characterized byelemental analysis and 1H- and 31P-NMR. Spectral dataare consistent with those for analogous compoundswith chelating dppe [16]. The methylplatinum resonanceis coupled with both phosphorus atoms and showsplatinum satellites. The coupling of the imine hydrogento platinum is considerably reduced (J(Pt�H)=8 Hz).In the 31P-NMR spectrum, two resonances due to thenon-equivalent phosphorus atoms appear and J(P�Pt)values (1660 and 2233 Hz) are consistent with thepresence of carbon atoms trans to the phosphorus. Thebigger value is assigned to the phosphorus trans tothiophene, due to the low trans influence of this group[9].

2.3. Oxidati6e addition reactions

It is generally accepted that the oxidative addition ofalkyl halides to platinum(II) compounds give trans

stereochemistry, although products arising from cis ox-idative addition can be formed in a subsequent isomer-ization process [3,8]. There is an increasing interest forthe potential stereoselectivity of oxidative addition ofalkyl halides to chiral cyclometallated platinum(II)compounds. Compounds containing the cyclometal-lated chiral imine 3-((S)-PhCHMeNCH)C4H2S are ade-quate substrates for such a study since the platinumcenter is expected to have a high electronic density.Moreover, the results obtained when either a SMe2 or aphosphine ligand complete the coordination sphere ofthe platinum could be compared.

Assuming a trans addition, two diastereoisomers (C,S) and (A, S), in which C/A represents the absolutestereochemistry (clockwise and anticlockwise) at theplatinum and S describes the chirality at carbon arepossible. We have reported previously that the oxida-tive addition of methyl iodide to [PtMe2{(S)-PhCHMeNCHC5H4N}], containing a [N, N %] chelateligand [17], and to the cyclometallated compound[PtMe{(S)-PhCHMeNCHC6H3F-2}PPh3] gave [7], ineach case, two diastereoisomers in nearly equalamounts (1:1 and 1.25:1, respectively).

It has been reported previously for compounds[PtMe{3-(PhCH2NCH)C4H2S}L] (L=SMe2, PPh3),that the oxidative addition takes place with trans stere-ochemistry, and is followed by isomerization of theresulting platinum(IV) compound. The isomerization,shown in reaction (1), should proceed through a disso-ciative pathway to yield a five-coordinate intermediate,which rearranges in order to minimize steric effects inthe final platinum(IV) compound. For the bulky PPh3

ligand, isomerization is completed within a few hours,while for SMe2, an equilibrium mixture of both isomersis attained. Such an isomerization should lead in thiscase to a new pair of diastereoisomers.


As shown in Scheme 2, the reaction of [PtMe{3-((S)-PhCHMeNCH)C4H2S}SMe2] (2) with methyl iodide inacetone at room temperature gave a mixture of twopairs of diastereoisomers (6a/6a% and 6b/6b%) of thecyclometallated platinum(IV) compound [PtMe2I{3-((S)-PhCHMeNCH)C4H2S}SMe2] (6). From the2J(H�Pt) values for the methyl groups, a fac-PtC3

structure is assigned to all isomers. Isomers 6a/6a% differfrom isomers 6b/6b% in having a methyl group trans toI or trans to SMe2, respectively. In agreement withprevious studies, the resonances at lower d were as-signed to axial methyl groups trans to iodide (isomers

6a/6a%). When a 1H-NMR was registered just afteradding methyl iodide to a solution of 2 in deuteratedacetone, the isomers 6a/6a% and 6b/6b% were detected inthe same relative amounts as in the preparative synthe-sis and their ratio remained constant in solution. Themixture of isomers is composed as follows: 6a (19.4%),6a% (9.3%), 6b (38.9%), and 6b% (32.4%). Thus, the mainproducts are the pair of diastereoisomers 6b/6b% arisingfrom isomerization of the initially formed 6a/6a%. Theratio 6a:6a%=2.1:1 indicates a significant degree ofenantioselectivity in the initial trans oxidative addition,although subsequent isomerization yields nearly equalamounts of both diastereoisomers (6b:6b%=1.2:1).

When the mixture of isomers 6b/6b% was treated withPPh3 in acetone, the substitution reaction of SMe2 forPPh3 yielded isomers 7b/7b% in which the triphenylphos-phine is trans to a methyl group, in the ratio 1.2:1, asconfirmed by 31P-NMR spectroscopy.

The reaction of racemic [PtMe{3-(PhCHMeNCH)-C4H2S}SMe2] (2%) with methyl iodide was also moni-tored by 1H-NMR. Again, four sets of resonances inthe same ratio as for chiral compound 2 are observedand assigned to the two pairs of diastereoisomers, eachwith its enantiomer.

The reaction of [PtMe{3-((S)-PhCHMeNCH)-C4H2S}PPh3] (3) with methyl iodide in acetone at roomtemperature was monitored by 1H- and 31P-NMR. Inthe early stages of the reaction, resonances assigned toa pair of diastereoisomers (7a/7a%) of the platinum(IV)compound [PtMe2I{3-((S)-PhCHMeNCH)C4H2S}-PPh3] appeared in a ratio 2.4:1 in the 31P-NMR, to-gether with signals due to unreacted platinum(II) com-pound 3. In the corresponding 1H-NMR, only theresonances due to the major of these isomers could beassigned unambiguously. As the reaction proceeded,resonances due to a second set of platinum(IV)diastereoisomers (7b/7b%) appeared and fully replacedthe former resonances within 4 h. The isomer 7a (or7a%) displays two methylplatinum resonances which ap-pear as doublets due to coupling to the phosphorusatom and with similar 2J(HPt) values (67 and 68 Hz,respectively). As for analogous cyclometallated com-pounds reported previously, the resonance at higherfields is assigned to the axial methyl. A similar patternis observed for isomers 7b/7b%, except for the fact that areduced coupling to platinum (2J(HPt)=60 Hz) is nowobserved for the axial methyl, which suggests a transarrangement of the axial methyl and the PPh3. 31P-NMR supported the successive formation of two differ-ent isomers, since the initial resonances assigned to7a/7a% decreased its intensity, while two new resonancesdue to the pair of diastereoisomers 7b/7b% grew. Theintensities of the signals in both 1H- and 31P-NMRindicate that the ratio 7b:7b% is 2.2:1.

The reaction of racemic [PtMe{3-(PhCHMe-NCH)C4H2S}PPh3] (3%) with methyl iodide was alsoScheme 2.


Scheme 3.

ously [7]. The bulk of ligand L does not significantlyaffect the ratio of the diastereoisomers formed initiallybut it is a decisive factor in the ratio of the diastereoiso-mers arising from the subsequent isomerization process.While for the bulky PPh3 derivatives, the proportion ofthe diastereoisomers is practically maintained (7b:7b%=2.2:1), for SMe2 an equilibration of the diastereoiso-mers occurs (6b:6b%=1.2:1).

The diastereomeric ratios obtained for 6a/6a% and7a/7a% are similar to those reported for the oxidativeaddition of methyl iodide to compound [PtMe{trans-1-(N�CHC6H4)-2-(N�CHC6H5)C6H10}] containing a [C,N, N%] tridentate ligand [8], in spite of the fact that thecompounds reported here have the chiral center in adangling benzyl group two atoms away from the plat-inum center.

3. Experimental

3.1. Instrumentation

1H- and 31P{1H}-NMR spectra were recorded byusing Varian Gemini 200 (1H, 200 MHz), Varian 500(1H, 500 MHz) and Bruker 250 (31P, 101.25 MHz)spectrometers, and referenced to SiMe4 (1H) and H3PO4

(31P). d values are given in ppm and J values in Hz. IRspectra were recorded as KBr disks on a Nicolet 520FTIR spectrometer. Microanalyses and mass spectra(CI and FAB) were performed by the Serveis Cientıfico,Tecnics de la Universitat de Barcelona.

3.2. Preparation of the compounds

Compound [Pt2Me4(m-SMe2)2] was prepared as re-ported [21].

3.2.1. Synthetic procedure for the compounds 1 and 23-((S)-PhCHMeNCH)C4H3S (1) was prepared by the

reaction of 0.5 g (4.46 mmol) of 3-tiophenecarboxalde-hyde with the equimolar amount of (S)-methylbenzy-lamine (0.54 g) in refluxing ethanol. After 4 h, thesolvent was removed in a rotary evaporator to yield awhite solid. Yield 0.8 g (83%). Racemic 3-(PhCH-MeNCH)C4H3S (1%) was prepared in an analogous wayusing (9 )-methylbenzylamine. 1H-NMR (200 MHz,CDCl3: d=1.58 [d, J(Ha�Hb)=7, Ha]; 4.48 [q,J(Ha�Hb)=7, Hb]; {7.34 [m]; 7.60 [m, 1H], aromatics};8.38 [s, Hc].

[PtMe{(3-((S)-PhCHMeNCH)C4H2S}SMe2] (2) wasobtained by adding a solution of 75 mg (3.5×10−4

mol) of the imine 1 in acetone (10 ml) to a solution of100 mg (1.74×10−4 mol) of compound [Pt2Me4(m-SMe2)2] in acetone (10 ml). The mixture was stirred for1 h and the acetone was removed in a rotary evapora-tor. The residue was washed with hexane and dried in

monitored by 1H- and 31P-NMR and the results wereidentical to those observed for the chiral compound 3.

Compounds [PtMe{3-((S)-PhCH2NCH)C4H2S}P(2-MeC6H4)3] (4) and [PtMe{3-((S)-PhCH2NCH)C4H2S}-(Ph2PCH2CH2PPh2)] (5) failed to react with methyliodide under the same experimental conditions used forthe reactions of compounds 2 and 3. The lack ofreactivity of compound 4 can be related to the resultsreported for analogous iridium compounds [18], forwhich the crystal structure revealed that one of theortho methyl groups in the phosphine is located abovethe coordination plane and isolates the central atomfrom attacking molecules. As for 5, the decrease inelectronic density at the platinum when the imine nitro-gen is replaced by a phosphorus atom may account forthe result obtained.

As shown in Scheme 3, the reactions of ethyl iodideand benzyl bromide with compound [PtMe{3-((S)-PhCHMeNCH)C4H2S}PPh3] (3) produced platinum(II)compounds [PtI{3-((S)-PhCHMeNCH)C4H2S}PPh3](8) and [PtBr{3-((S)-PhCHMeNCH)C4H2S}PPh3] (9),respectively. The formation of a small amount of metal-lic platinum indicates some degree of decomposition inthis process. Although it is most likely that compounds8 and 9 arise from oxidative addition of the alkyl halidefollowed by reductive elimination, the correspondingplatinum(IV) compounds could not be detected whenthe reaction was monitored by 31P-NMR.

In the 1H-NMR of compounds 8 and 9, the couplingof the imine nitrogen to phosphorus, within the samerange as reported for analogous palladium compounds[19,20], indicates a trans arrangement of N and Patoms, which is also supported by the J(P�Pt) values.

In conclusion, a higher degree of stereoselectivity isobtained for the oxidative addition of methyl iodide tothienyl derivatives [PtMe{3-((S)-PhCHMeNCH)-C4H2S}L] (L=SMe2, 6a:6a%=2.1:1; PPh3, 7a:7a%=2.4:1) than for the phenyl analogues reported previ-


vacuum. Yield 120 mg (71%). Racemic [PtMe{(3-(PhCHMeNCH)C4H2S}SMe2] (2%) was prepared from1% in an analogous way. 1H-NMR (200 MHz, CDCl3):d=1.09 [s, 2J(Pt�H)=79, Mea]; 1.71 [d, J(Hc�Hd)=7,Hc]; 1.93 [s, 3J(Hb�Pt)=32, Hb]; 5.28 [q, J(Hc�Hd)=6,Hd]; {7.18 [d, 4J(Pt�H)=35, J(H�H)=5]; 7.30 [m],aromatics}; 8.49 [s, 3J(Pt�He)=51, He]. Anal. Found:C, 39.2; H, 4.3; N, 2.9. Calc. for C16H21NPtS2: C, 39.50;H, 4.35; N, 2.88%.

3.2.2. Synthetic procedure for the phosphine deri6ati6es[PtMe{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (3) was

obtained by the reaction of 50 mg (1.03×10−4 mol) ofcompound 2 with 25 mg (0.95×10−4 mol) of PPh3 inacetone. After continuous stirring for 2 h, the solventwas removed in a rotary evaporator and the resultingyellow solid was filtered, washed with hexane, anddiethylether and dried in vacuum. Yield 55 mg (78%).Racemic [PtMe{(3-(PhCHMeNCH)C4H2S}PPh3] (3%)was prepared from 2% in an analogous way. 1H-NMR(200 MHz, CDCl3): d=0.91 [d, 2J(Pt�H)=80,3J(P�H)=8, Mea]; 1.05 [d, J(H�H)=7, Meb]; 4.40 [q,J(H�H)=7, Hc]; {6.93 [m, 2H]; 7.18 [m, 5H], 7.33 [m,10H]; 7.68 [m, 5H], aromatics}; 8.27 [s, 3J(Pt�Hd)=53,Hd]. 31P-NMR (101.26 MHz, CDCl3): d=31.29[J(Pt�P)=2586]. Anal. Found: C, 55.8; H, 4.4; N, 2.1.Calc. for C32H30NPPtS: C, 55.97; H, 4.40; N, 2.04%.

[PtMe{(3-((S)-PhCHMeNCH)C4H2S}P(2-MeC6H4)3](4) was prepared in an analogous way using the corre-sponding phosphine. Yield 60 mg (80%). 1H-NMR (200MHz, CDCl3): major isomer: d=0.05 [d, 3J(P�H)=7,Meb]; 0.99 [d, 2J(Pt�H)=82, 3J(P�H)=8, Mea];{1.60[s], 1.95[s], 2.97[s], He}; 4.65 [q, J(H�H)=7, Hc];8.04 [s, 3J(Pt�Hd)=52, Hd]; 9.22 [dd, J(H�H)=16; 7,Har]. 31P-NMR (101.26 MHz, CDCl3): d=25.17[J(Pt�P)=2473]; minor isomer: d=0.96 [d,2J(Pt�H)=82, 3J(P�H)=8, Mea]; 1.48 [d, 3J(P�H)=7,Meb]; {1.57[s], 1.95[s], 2.81[s], He}; 8.37 [s, 3J(Pt�Hd)=52, Hd]; 9.15 [dd, J(H�H)=16; 7, Har]. 31P-NMR(101.26 MHz, CDCl3): d=26.12 [J(Pt�P)=2479].Anal. Found: C, 57.6; H, 4.9; N, 1.9. Calc. forC35H36NPPtS: C, 57.68; H, 4.98; N, 1.92%.

[PtMe{(3-((S)-PhCHMeNCH)C4H2S}Ph2PCH2CH2-PPh2] (5) was obtained by the reaction of 50 mg(1.03×10−4 mol) of compound 2 with 41 mg (1.03×10−4 mol) of dppe in acetone. After continuous stirringfor 6 h, the solvent was removed in a rotary evaporatorand the resulting white solid was filtered, washed withhexane, and diethylether and dried in vacuum. Yield 60mg (71%). 1H-NMR (200 MHz, CDCl3): d=0.64 [t,2J(Pt�H)=69, 3J(P�H)=7, Mea]; 1.39 [d, J(H�H)=7,Meb]; 2.25 [m, CH2P], 4.09 [q, J(H�H)=7, Hc]; {7.21[m]; 7.35 [m], 7.49 [m]; 7.72 [m], aromatics}; 8.38 [s,3J(Pt�Hd)=8, Hd]. 31P-NMR (101.26 MHz, CDCl3):d=47.38 [J(Pt�P)=2233], 44.28 [J(Pt�P)=1660].Anal. Found: C, 58.2; H, 4.8; N, 1.6. Calc. forC40H39NP2PtS: C, 58.39; H, 4.78; N, 1.70%.

3.2.3. Synthetic procedures for the oxidati6e additionreactions

An excess of methyl iodide (0.1 ml) was added tosolutions of 50 mg of the compounds 2 and 3 inacetone. The mixtures were stirred for 4 h, and thesolvent was removed under vacuum to yield light yel-low solids.

[PtMe2I{(3-((S)-PhCHMeNCH)C4H2S}SMe2] (6a/6a %/6b/6b %). Yield 50 mg (77%). 1H-NMR (500 MHz,acetone-d6): (6a/6a%), major isomer: d=0.59 [s,2J(Pt�H)=68, Meb]; 1.41 [s, 2J(Pt�H)=68, Mea]; 1.73[d, J(H�H)=7, Hd]; 5.71 [qd, J(H�H)=7, J(H�H)=1.5, He]; 8.67 [d, 3J(Pt�H)=45, J(H�H)=1.5, Hf];minor isomer: d=0.81 [s, 2J(Pt�H)=68, Meb]; 1.54 [s,2J(Pt�H)=68, Mea]; 1.83 [d, J(H�H)=7, Hd]; 5.61 [q,J(H�H)=7, He]; 8.10 [d, 3J(Pt�H)=45, J(H�H)=1,Hf]. (6b/6b%), major isomer: d=1.35 [s, 2J(Pt�H)=70,Meb]; 1.63 [s, 2J(Pt�H)=68, Mea]; 1.74 [d, J(H�H)=7,Hd]; 6.14 [q, J(H�H)=7, He]; 8.40 [d, 3J(Pt�H)=44,J(H�H)=2, Hf]; minor isomer: d=1.15 [s, 2J(Pt�H)=70, Meb]; 1.61 [s, 2J(Pt�H)=68, Mea]; 1.76 [d,J(H�H)=7, Hd]; 1.98 [s, 3J(Pt�H)=12, Hc]; 2.14 [s,3J(Pt�H)=13, Hc]; 6.22 [q, J(H�H)=7, J(Pt�H)=6.5,He]; 8.52 [d, 3J(Pt�H)=45, J(H�H)=1, Hf]. Anal.Found: C, 32.4; H, 3.8; N, 2.2. Calc. for C17H24INPtS2:C, 32.49; H, 3.85; N, 2.23%.

[PtMe2I{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (7b/7b %). Yield 45 mg (74%). Major isomer: 1H-NMR (500MHz, acetone-d6): d=0.82 [d, 2J(Pt�H)=60,J(H�P)=7, Meb]; 1.60 [d, 2J(Pt�H)=69, J(H�P)=7,Mea]; 1.05 [d, J(H�H)=7, Hc]; 6.02 [q, J(H�H)=7,J(Pt�H)=7, Hd]; {6.54 [d, J(H�H)=7], 7.10 [d,J(H�H)=5.5, J(H�Pt)=25], aromatics}, 8.75 [d,3J(Pt�H)=48, J(H�H)=2, He]. 31P-NMR (101.26MHz, acetone-d6): d= −10.45 [J(Pt�P)=983]. Minorisomer: 1H-NMR (500 MHz, acetone-d6): d=1.35 [d,2J(Pt�H)=60, J(H�P)=7, Meb]; 1.69 [d, 2J(Pt�H)=70, J(H�P)=8, Mea]; 1.82 [d, J(H�H)=7, Hc]; 5.72 [q,J(H�H)=6, Hd]; {6.98 [d, J(H�H)=5], 7.03 [d,J(H�H)=5], aromatics}, 7.78 [s, 3J(Pt�H)=45, He].31P-NMR (101.26 MHz, acetone-d6): d= −10.60[J(Pt�P)=1012]. Anal. Found: C, 47.4; H, 4.0; N, 1.9.Calc. for C33H33INPtS: C, 47.83; H, 4.01; N, 1.69%.

The reactions of compounds 2 and 3 with methyliodide were monitored by NMR in the following way;10 ml of methyl iodide were added to 20 mg of thecorresponding compound dissolved in 0.6 ml of ace-tone-d6 in a 5 mm NMR tube and spectra were taken.

[PtMe2I{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (7a/7a %). [PtMe2I{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (7a/7a%) was characterized spectroscopically in solution.Major isomer: 1H-NMR (200 MHz, acetone-d6): d=0.21 [d, 2J(Pt�H)=66, J(H�P)=7, Meb]; 1.46 [d,


Table 2Crystallographic data and details of the refinements for compound 2

C16H21NPtS2FormulaFormula weight 486.55

OrthorhombicCrystal systemP212121Space group

a (A, ) 11.191(2)11.974(7)b (A, )12.321(8)c (A, )

a (°) 9090b (°)90g (°)

V (A, 3) 1651(2)2.076Dcalc (g cm−3)4Z

F(000) 9360.1×0.1×0.2Crystal size (mm3)0.71069l(Mo–Ka) (A, )

T (K) 293(2)2321Reflections collected0.0321R [I\2s(I)]0.0673Rw(F2)183Refined parameters0.0max. shift/estimated S.D.0.681 and −0.680max. and min. difference peaks (e A, −3)

method. Intensities were collected with graphitemonochromatized Mo–Ka radiation, using v/2u scan-technique. 2321 reflections were measured in the range2.37BuB29.95°; 2299 were non-equivalent by symme-try and 2083 were assumed as observed applying thecondition [I\2s(I)]. Three reflections were measuredevery 2 h as orientation and intensity controls; signifi-cant intensity decay was not observed. Lorentz polariza-tion and absorption corrections were made. Furtherdetails are given in Table 2.

3.3.2. Structure solution and refinementThe structure was solved by direct methods, using

SHELXS computer program [22], and refined by the full-matrix least-squares method, with the SHELX-93 com-puter program [23] using 2249 reflections (very negativeintensities were not assumed). The function minimizedwas � w ��Fo�2− �Fc�2�2, where w= [s2(I)+(0.0326P)2]−1, and P= (�Fo�2+2�Fc�2)/3. f, f % and f %%were taken from international tables of X-ray crystal-lography [24]. The chirality of the structure was definedfrom the Flack coefficient [25], which is equal to 0.03(2)for the given results. All hydrogen atoms were com-puted and refined with an overall isotropic temperaturefactor using a riding model. Further details are given inTable 2.

4. Supplementary material

Crystallographic data for the structural analysis hasbeen deposited with the Cambridge CrystallographicData Centre, CCDC no. 140492 for compound 2.Copies of this information may be obtained free ofcharge from The Director, CCDC, 12 Union Road,Cambridge CB2 1EZ, UK (fax: +44-1223-336033; e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk).

Acknowledgements

We acknowledge financial support from the DGICYT(Ministerio de Educacion y Cultura, Spain) and fromthe Generalitat de Catalunya.

References

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2J(Pt�H)=68, J(H�P)=7, Mea]; 1.55 [d, J(H�H)=7,Hc]; 5.35 [m, Hd]; 6.63 [d, J(H�H)=6, aromatics], 8.66[d, 3J(Pt�H)=46, He]. 31P-NMR (101.26 MHz, ace-tone-d6): d= −6.03 [J(Pt�P)=1544]. Minor isomer:31P-NMR (101.26 MHz, acetone-d6): d= −3.92[J(Pt�P)=1553].

An excess of ethyl iodide or benzylbromide (0.1 ml)was added to solutions of 50 mg of compound 3 in ace-tone. The mixtures were stirred for 48 h, and the solventwas removed under vacuum to yield yellow solids.

[PtI{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (8). 1H-NMR (200 MHz, acetone-d6): d=1.73 [d, 2J(H�H)=7,Mea]; 6.81 [m, Hb]; {7.35–7.50[m]; 7.71–7.82[m], aro-matics}; 7.95 [d, 3J(H�Pt)=89, J(H�P)=9.5, Hc]. 31P-NMR (101.26 MHz, acetone-d6): d=13.65[J(Pt�P)=3786]. Anal. Found: C, 46.5; H, 3.6; N, 1.7.Calc. for C31H27INPPtS: C, 46.63; H, 3.41; N, 1.75%.

[PtBr{(3-((S)-PhCHMeNCH)C4H2S}PPh3] (9). 1H-NMR (200 MHz, acetone-d6): d=1.75 [d, 2J(H�H)=7,Mea]; 6.50 [m, Hb]; {7.26–7.46[m]; 7.70–7.76[m],aromatics}; 7.95 [d, 3J(H�Pt)=90, J(H�P)=9.5,Hc]. 31P-NMR (101.26 MHz, acetone-d6): d=15.02[J(Pt�P)=3836].

3.3. X-ray structure analysis

3.3.1. Data collectionA prismatic crystal was selected and mounted on an

Enraf–Nonius CAD4 diffractometer. Unit cell parame-ters were determined from automatic centering of 25reflections (12BuB21°) and refined by least-squares


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oxidative addition of alkyl halides to chiral cyclometallated platinum(ii) complexes with thienyl...

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